Remotely controlled modulating system



March 16, 1965 w. A. MORGAN 3,174,110

REMOTELY CONTROLLED MODULATING SYSTEM Filed Aug. 24, 1962 Fl (3 I 62 6O g I I 58 54 7 BISIABLE PULSE VARIABLE MULTIVIBRATOR FORMER A DC VOLTAGE SOURCE AUDIO AMPLIFIER I i I --I4 1 "A l 20 I I 42 44 4e 1 I\.- I2 I 2 I 22 l )X FREQUENCY PULSE VARIABLETIME oou DELAY 24 BLER FORMER CIRCUIT f 48 so 34 I SIGNAL 40 GENERATOR I 70 l l l l I 28 11,8! 16 74 ea ez MAGNET POWER SUPPLY RECORDER AUDIO AMPLIFIER i l 48 l WALTER A. MORGAN, BY 1 ATTORNEY.

FIG. 2.

United States Patent 3,174,110 REMGTELY CGNTRQLLED MODULATING SYSTEM Walter A. Morgan, Baytown, Ten, ass lgnor, by mesne assignments, to Esso Research and Engineering (Tornpany, Elizabeth, NJ a corporation of Delaware Filed Aug. 24, 1962, Ser. No. 219,258 4 Claims. (0. 330-) This invention relates to remotely controlled means for modulating a variable such as a current, voltage, or frequency.

The electrical system to be described herein has wide application. For example, my new modulating system can be used to modulate the electron beam intensity in a mass spectrometer ion source in order to produce a modulated signal at the ion collector so that A.C. amplification and detection schemes can be employed.

My new system can also be used for the on-off control of the ion beam in a particle accelerator used for neutron activation studies so that the activation level of short half-life materials can be counted during the OE periods of the ion beam.

A further use of this new system is in the modulation of the ion beam energy in a particle accelerator used to produce neutrons by the deuterium-tritium resonance reaction followed by phase sensitive detection of the resulting variation in neutron intensity in order to produce a controlled signal for the automatic control of the total deuteron energy at the optimum value for high neutron production and long target life.

Some of the many advantages of my new remotely controlled modulating system are the following:

(1) The system has no direct mechanical or electrical interconnection between the controlled variable and a phase sensitive detection system. Thus, large potential differences or extreme environmental conditions can exist between the point of application of the controlled variable and the detector without any damaging effect upon the operation of the system.

(2) The system will operate over a wide range of modulation frequencies.

(3) The modulator control signal is transmitted by means other than high-frequency radio signals. Hence, the usual high-frequency radio interference is eliminated.

Briefly described, the new system includes an electric signal generator which generates signals having a predetermined frequency. The signals from the electric signal generator are fed to a transducer which converts the electric signals into remotely detectable signals. These signals are detected by a second transducer remotely located from the first transducer. The second transducer converts the remotely detectable signals into corresponding electric signals. These electric si nals are fed to a means for producing a modulation signal. The modulation signal applies a fluctuating signal to a controlled variable. Themodulated controlled variable is detected. A direct current output signal is obtained which is proportional to the fluctuating component of the modulated controlled variable.

The invention, as well as its many advantages, will be further understood by reference to the following detailed description and drawings in which:

FIG. 1 is a diagram of a simplified mass spectrometer equipped with the remotely controlled modulating system of my invention; and

FIG. 2 is a simplified drawing showing different types of transducers from those shown in FIG. 1.

Referring to the drawings and more particularly to FIG. 1, my new remotely controlled modulatiru system is shown applied to a mass spectrometer such as that dis- 3, 1 74,1 10 Patented Mar. 16, 1965 ice molecules in ionization chamber 12 are ionized in the ionization chamber 112.

An electrostatic field-impressing electric circuit is provided for accelerating the ionized particles through exit slit 16. This circuit includes a variable DC. voltage source 18 which feeds a voltage through lines 20 and 22 to apply a difference in potential V between the chamber 12 and accelerating electrode 24 After the ionized'pa'rticles have accelerated, they are resolved into separate homogeneous beams according to their mass to charge ratio by means of a magnetic field produced between the poles or" the electromagnet 26. The strength of the magnetic field which exists between the poles of the electromagnet 26 is a function of the current flowing through the winding 28. By maintaining the magnetic field constant and varying the accelerating potential V, the resolved ion beams are caused to move across the resolving slit 29. Those ions which pass through the slit impinge on the collector electrode 36.

A retarder electrode 34 is placed in the analyzer just after the ionization chamber 12. In order to obtain higher resolution than formerly obtainable, it is desired to apply a fluctuating or AC. modulating signal to the retarder electrode 34.

The modulating system includes a signal generator 40. The signal generator 40 produces an electric signal having a predetermined frequency. The signal generator may be a free-running multivibrator circuit for producing a square wave output signal. The frequency from signal generator 4t} may be made to vary from 0 to 1,090 cycles per second by simultaneously increasing or decreasing the products of resist0r-capacitor components (not shown) located in the signal generator circuit.

The output from the signal generator 40 is fed to a frequency doubler 42, a pulse former 44, and a variable time delay circuit 46.

The pulses from the variable time delay circuit 46 are fed through amplifier 48 to a transducer 50. The transducer 50 converts the electric signals from the amplifier 43 into corresponding remotely detectable signals. The transducer may, for example, be a transmitting speaker, such as shown in FIG. 1, which converts the electric signals into acoustic pulses or, if desired, the transducer may be a light source 52, such as shown in FIG. 2, for converting the electric signals into corresponding light pulses.

A second transducer such as a microphone 54 (see FIG. 1) or a photosensitive cell 56 (see FIG. 2) for reoonverting the remotely detectable signals into corresponding electric signals is remotely located from the speaker 59 or light source 52, respectively. The corresponding electric signals are fed to an audioamplifier 53, then to pulse former 60, and then to bistable multivi=brator 62. The pulse former 6t) shapes the amplified signals into pulses suitable for use in triggering the bistable mult-ivibrator 62 to cause it to flip from one stable state to the other stable state each time an acoustical or optical pulse impinges upon the microphone 54 or photosensitive cell 56, respectively.

The frequency doubler 4-2 doubles the frequency from the signal generator 40. The output from pulse former 60 has a frequency equal to the frequency from the frequency doubler 42. Since the bistable multivibrator 62 is trigged from one stable state to the other stable state each time -a pulse is received by the bistable multiby the time delay circuit 46 and the control link between the transducers.

The output from the bistable multivibrator 62 is applied to the retarder electrode 34. Thus, the ion beam current detected by collector electrode 30 contains a steady component and a fluctuating or A.C. component. This current is fed from collector electrode 30 through amplifier 64 and condenser 66 to a chopper switch 68.

The switch 68 is operated at the same frequency as the frequency from the signal generator 40. This is accomplished by feeding the signals from the signal gen erator 40 through an amplifier 70' to a phase sensitive coil 72 which operates switch 68.

The'function of the switch 68 is to provide phase sensitive detection of the A.C. component in the output signal from amplifier 64. Capacitor 74 in parallel with the voltage divider resistors 76 and 78 filters the pulsating D.C. signal obtained from the switch 68 through contacts 81 and 82 and provides a filtered D.C. voltage proportional to the inphase component of the AC. signal produced at the output of amplifier 64. The voltage across resistor 78 may be indicated on a recorder Si or used to actuate a control system.

in operation, the amount of time delay is adjusted bymeans of the variable time delay circuit 46. Time delay adjustment potentiometers (not shown) are included in the variable time delay circuit 46 to permit the pulses to be delayed from to approximately 360 with respect to the output signal from the signal generator 49. The amount of time delay inserted by the variable time delay circuit 46 is adjusted until the input signal to the retarder electrode 34 is brought into phase with the switching action of the phase sensitive detector switch 68. When the signals are inphase, a DC. output signal proportional to the AC. component of the modulated ion beam current will be produced.

I claim:

1. A modulating system comprising: an electric signal generator for generating signals having a predetermined frequency; a first transducer responsive to signals from the signal generator and adapted to convert the generated signals into remotely detectable signals; a second transducer remotely located from the first trans ducer and adapted. to detect the remotely detectable signals and produce corresponding electric signals; means responsive to said corresponding electric signals and adapted to produce a modulation signal for a controlled variable; means for detecting the modulated controlled variable in synchronism with the modulation signal; and means for receiving said detected modulated controlled variable and producing a direct current output signal proportional to the alternating current component of the modulated controlled variable.

2. A modulating system comprising: an electric signal generator for generating signals having a predetermined frequency; a first transducer responsive to signals from the signal generator and adapted to convert the generated signals into remotely detectable signals; a second transducer remotely located from the first transducer and adapted to detect the remotely detectable sig- 4 nals and produce corresponding electric signals; means responsive to said corresponding electric signals and adapted to produce a modulation signal for a control-led variable; means for detecting the modulated controlled variable including a switch operated by said signal generator; a variable time delay circuit in the electrical path roin said signal generator to said first transducer for bringing the modulation signal into phase with the sig-. nal from the signal generator; and means for receiving said detected modulated controlled variable and proalternating current component of the modulated controlled variable.

3. A modulating system comprising: an electric signal generator for generating signals having a predetermined frequency; a frequency doubler for receiving said signals and doubling the frequency thereof; a variable time delay circuit for receiving the signals from the frequency doubler; a first transducer responsive to signals from the variable time delay circuit and adapted to convert said signals into corresponding remotely detectable signals; a second transducer remotely located from the first transducer and adapted to detect the remotely detectable signals and produce corresponding electric signals; a bistable multivibrator for receiving .the signals from said second transducer and producing a modulation signal for a controlled variable and having a frequency the same 'as the frequency of the signals from the signal generator; means for detecting the modulated controlled variable including a switch operated by said signal generator; and means for receiving said detected modulated controlled variable and producing a direct current output signal proportional to the alternating current component of the modulated controlled variable.

4. A modulating system comprising: an electric sig nal generator for generating signals having a predetermined -frequency; a frequency doubler for receiving said signals and doubling the frequency thereof; a pulse former for receiving the signals from the frequency doubler and forming pulses therefrom; .a variable time delay circuit for receiving the pulses from the pulse former; a first transducer responsive to the pulses from the variable time delaycircuit and adapted to convert said pulses into corresponding remotely detectable signals; a second transducer remotely located from the first transducer and adapted to detect the remotely detectable signals and produce corresponding electric signals; a second pulse former for receiving the electric signals from the second transducer; a bistable multivibrator for receiving the pulses from the second .pulse former and producing a modulation signal for a controlled variable and having a frequency the same as the frequency of the signals from the signal generator; means for detecting the modulated controlled variable including a switch operated by said signal generator; and means for receiving said detected modulated controlled variable and producing a direct current output signal proportional to the alternating current component of the modulated controlled variable.

References Cited in the file of-this patent UNITED STATES PATENTS 

1. A MODULATING SYSTEM COMPRISING: AN ELECTRIC SIGNAL GENERATOR FOR GENERATING SIGNALS HAVING A PREDETERMINED FREQUENCY; A FIRST TRANSDUCER RESPONSIVE TO SIGNALS FROM THE SIGNAL GENERATOR AND ADAPTED TO CONVERT THE GENERATED SIGNALS INTO REMOTELY DETECTABLE SIGNALS; A SECONE TRANSDUCER REMOTELY LOCATED THE REMOTELY DETECTABLE SIGDUCER AND ADAPTED TO DETECT THE REMOTELY DETECTABLE SIGNALS AND PRODUCE CORRESPONDING ELECTRIC SIGNALS; MEANS RESPONSIVE TO SAID CORRESPONDING ELECTRIC SIGNALS AND ADAPTED TO PRODUCE A MODULATION SIGNAL FOR A CONTROLLED VARIABLE; MEANS FOR DETECTING THE MODULATED CONTROLLED VARIABLE IN SYNCHRONISM WITH THE MODULATION SIGNAL; AND MEANS FOR RECEIVING SAID DETECTED MODULATED CONTROLLED VARIABLE AND PRODUCING A DIRECT CURRENT OUTPUT SIGNAL PROPORTIONAL TO THE ALTERNATING CURRENT COMPONENT OF THE MODULATED CONTROLLED VARIABLE. 